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# Guide to Enums in the Python Programming Language
- URL: https://sudosecurity.org/enums-in-python/
- Published: 2023-06-10T02:17:00.000Z
- Updated: 2026-07-17T10:51:23.000Z
- Author: Traven
- Tags: Programming, Python, Tutorials

Enumerations (`Enums`) provide a powerful way to represent a set of named values. Enums bring clarity, maintainability, and readability to code by replacing numeric or string constants with more meaningful named constants.

The most common way I see people use `enums` is in roles in a web application such as a forums, blog, or something that has different access levels. Here is a common code sample of what this could look like.

```Python
from enum import Enum

class UserRole(Enum):
    ADMIN = "admin"
    USER = "user"
    EDITOR = "editor"
    GUEST = "guest"
```

In the example, `UserRole` is an `enum` with 4 member roles: `ADMIN`, `USER`, `EDITOR`, and `GUEST`, each associated with a string value. 

Enums guarantee unique names by design. Each member of an `enum`is distinct and attempting to create multiple members with the same name will raise a `TypeError`.

```Python
from enum import Enum

class UserRole(Enum):
    ADMIN = "admin"
    USER = "user"
    EDITOR = "editor"
    GUEST = "guest"
    ADMIN = "super user"

# TypeError: Attempted to reuse key: 'ADMIN'
```

The `enum` module also has a decorator, `@unique`, that ensures that the enum should have a distinct name and values.

```Python
from enum import Enum, unique

@unique
class UserRole(Enum):
    ADMIN = "admin"
    USER = "user"
    EDITOR = "editor"
    GUEST = "guest"
    ADMIN = "super user"

# TypeError: Attempted to reuse key: 'ADMIN'
```

If the `enum` has duplicate values, then the `@unique` decorator generates a `ValueError`.

```Python
from enum import Enum, unique

@unique
class UserRole(Enum):
    ADMIN = "admin"
    USER = "user"
    EDITOR = "editor"
    GUEST = "guest"
    S_ADMIN = "admin"

# ValueError: duplicate values found in <enum 'UserRole'>: S_ADMIN -> ADMIN
```

## Accessing the `emun` Members

We can access the name and value of an `enum` member as attributes. 

```Python
print(UserRole.EDITOR)          # UserRole.EDITOR
print(UserRole.EDITOR.value)    # Editor
print(UserRole['ADMIN'])	# UserRole.ADMIN
```

## Iterating Over Enums

Iterating over `enums` is straightforward: the loop will output each member of the `UserRole` `enum`. 

```Python
for role in UserRole:
    print(f"Role Name: {role.name} - Value: {role.value}")
```

## Enum Comparisons

`Enums` supports comparisons both for equality and identity. Here is a code sample to show how this is done. 

```Python
print(UserRole.ADMIN == UserRole.ADMIN) # True
print(UserRole.ADMIN is UserRole.ADMIN). # True. 
```

## **Enums in Function Signatures**

From Python's latest versions, 3.10 and above, `enums` can be used directly in function signatures. This allows us to specify an `enum` as an argument or return type in function signatures. 

**Argument Type**: Specify the `enum` type as the type of function parameter.

```Python
def get_user_role(role: UserRole):
    return role.value
```

`Return Type`: `Enum` can be used as the `return` type of the function.

```Python
def my_function() -> UserRole:
    return UserRole.ADMIN
```

## **Advantages of Using Enums**

### **Improved Code Readability**

Enums provide meaningful names for values, making the code more self-explanatory. Instead of using numeric or [string](https://dzone.com/articles/python-f-strings?ref=sudosecurity.org) constants scattered throughout the code, enum members give descriptive names to the possible values. 

### **Enhanced Maintainability**

Enums make code more maintainable by centralizing the definition of possible values. If changes are needed, you only need to modify the enum definition rather than searching and updating occurrences throughout the code.

### **Expressive Intent**

Enums excel in revealing the intention of your code by providing names that distinctly reflect the purpose of the values. This feature contributes to making the code more expressive, enhancing its clarity. 

### **Prevention of Invalid Values**

Enums help prevent the use of invalid values by restricting the choices to the defined enum members. This reduces the chances of introducing bugs due to unexpected values. In our `User` role example, if we pass an invalid role value, the program raises a `ValueError`.

```Python
role = UserRole('s_admin')
# ValueError: 's_admin' is not a valid UserRole

role = UserRole('admin')
# <UserRole.ADMIN: 'admin'>
```

## **The Conclusion**

Enums in Python provide a clear and expressive way to represent fixed sets of values. They enhance code readability, prevent bugs by restricting variable values, and contribute to a more maintainable and self-documenting code.